Women of reproductive age, including adolescent girls, pregnant women in their second or third trimester, and lactating women constitute a high-risk group for morbidity attributable to the soil-transmitted helminths, primarily Trichuris and hookworm infections. WHO, among other global, regional and national organizations, recommends mass deworming targeted to this group in endemic areas where the prevalence of hookworm infection exceeds 20%. The research we propose will provide empirical evidence on which to guide health policy and program implementation for large-scale deworming programs targeting this at-risk group. Four objectives are identified: 1) to conduct a systematic review of inadvertent exposure to deworming in the first trimester of pregnancy; 2) to assess the receptiveness of adolescent girls of school- age to answer questions on pregnancy (to rule out deworming during the first trimester during school-based deworming programs); 3) to determine the stage of pregnancy at which women will first attend an antenatal care clinic; and 4) to determine the health impact, to mothers and babies, of deworming administered to women in-hospital, immediately after delivery. The results of this research will contribute to ensuring cost- effective and efficient deworming programs targeted to women of reproductive age and, ultimately, to reducing the disease burden of helminth infection in this vulnerable population.